Apparatus and method for triggering therapeutic shock waves

ABSTRACT

An instrument for therapeutic shock waves in which the shock waves are triggered in response to the patient&#39;s heartbeat cycle or to the patient&#39;s breathing cycle or both.

This application is a division of application Ser. No. 894,739 filedAug. 11, 1986 (now U.S. Pat. No. 4,685,461) which is a continuation ofapplication Ser. No. 722,126 filed Apr. 10, 1985 (now abandoned), whichlater was a continuation of application Ser. No. 443,567 filed Nov. 22,1982 (now abandoned).

The invention relates to a trigger for therapeutic shock waves, forinstance for comminuting kidney stones.

An instrument for the contactless comminution on concretions in bodiesof living tissue by means of shock waves is known (note U.S. Pat. No.3,942,531). In this instrument, electric discharges along a submergedspark gap generate shock waves in a focusing chamber, outside the body,the shock waves being focused on the concretion and comminuting it.These shock waves pass through the body tissue without damaging it.However, extrasystoles may be triggered in the stimulative phase of theheartbeat. Accordingly, the heart rhythm can be disturbed in patientswith circulatory problems. In that case adequate circulation of theblood no longer will be ensured. Moreover, care must be taken whenselecting the trigger time that the coordinated of the target, forinstance the kidney--which are periodicaliy changing due tobreathing--shall be as constant as possible at the time of the shockwave triggering in order to achieve a high impact probability.

It is an object of the present invention to provide an instrumentcorrelating the trigger time of the shock wave to the heart action insuch a manner that the heart rhythm cannot be disturbed.

This problem is solved by the invention by an instrument triggering theshock wave by the QRS peak of the EKG, or by triggering with a selectivetime-delay thereafter.

Another object of the invention is to correlate the trigger time of theshock waves with the patient's breathing cycle, so that the focus pointfor the shock waves may be related more precisely to the particularlocation within the patient's body where shock wave impact is desired,such as at the location of a stone to be comminuted. This object may berealized by sensing the patient's breathing cycle (as with a spirometeror respirometer) and using the sensed signal for enabling generation ofshock waves only during a selected portion of the patient's breathingcycle, such for example, as during the pause that follows exhalation.This feature may be used in conjunction with or separately from thefeature by which shock wave triggering is correlated with the patient'sheart rhythm.

One of the advantages of this invention is that shock waves can beapplied to patients with impaired blood circulation and that this groupof patients also can be spared surgical intervention. The physician isrelieved, by the automatic time correlation with the heartbeat orfurther body functions, from the task of matching the shock waveapplication to the body rhythms. This permits avoidance of erroneoussteps.

The invention will be further illustrated by reference to theaccompanying drawings, in which:

FIG. 1 shows the EKG voltages as function of time for normal heartbeat,

FIG. 2 is a block diagram of an instrument with further automation bytaking into account a second body function, in this case breathing, and

FIG. 3 is a diagrammatic representation of apparatus provided with ashock wave triggering system in accordance with the invention in whichthe matter to be treated by the shock waves is illustrated as aconcretion or stone within a patient's kidney.

Referring to FIG. 1, the terms P, Q, R, S, and T of the wave functionare conventional in medicine. The steepest rise occurs at the leadingedge of the QRS peak (FIG. 1). Point 2 shows a danger-free trigger timein the S-T internal of the patient's heartbeat cycle for applying shockwaves. The EKG is recorded in known manner, and a trigger pulse isobtained in known manner from the leading edge of the QRS peak and fedinto a delay system. This system is adjustable within the range from 0to 1000 msec and, depending on the time preselected by the physician(distance 1-2), delivers a trigger pulse to a spark gap, which isignited and then generates a shock wave.

Referring to FIG. 2, two test-signal pick ups, pick up 3 for tne EKG,and pick up 4 (such as a spirometer or respirometer) for the breathingmotion, feed their test values each to a pulse generator 5, 6. Thesegenerators can be so set that they will deliver a pulse for a specificphase of the test values, for instance 10 msec after the occurrence ofthe QRS peak or at the time of the breathing pause which followsexhalation. The pulse generators are connected to the input of an ANDgate 7. The output of the gate 7 is fed through a manual switch 8 to aspark gap.

A trigger pulse therefore arrives at the spark gap only when:

(a) the physician keeps the switch 8 closed,

(b) the breathing motion is null, and

(c) the QRS peak of the EKG has just occurred.

The overall system is depicted in FIG. 3. A shock wave generator 9,having a spark gap 10 for initiating shock waves and a curved reflectoror waveguide 11 for focusing the shock waved, is shown diagrammaticallyin association with a schematic representation of a human patient 12. Aconcretion or stone 13 to be comminuted is shown as being located in akidney, remote from the patient's heart and close enough to the lungarea to be subject to movements as the patient breathes. The curvedwaveguide 11 is preferably of elliptical configuration, as described inthe aforesaid U.S. Pat. No. 3,942,531, and it is intended that the sparkgap 10 be at one focal point of the ellipse and the concretion 13 at thesecond focal point of the ellipse, so that the shock wave energy will befocused on the concretion 13 to comminute it efficiently.

Pulses of energy for firing the spark gap 10 of the shock wave generator9 are passed to the shock wave generator by electrical conduit means 14under control of means 15 operatively connected to and governed byvarious control inputs which assure that the triggering of the shockwaves will not occur at the wrong moments as already explained above.That is, protection against extrasystole stimulation is provided bypreventing passage of a pulse to the generator means except at timeswhen both the physician has activated switch means 16 and the EKG signalpickup means 17 has provided an indication that a safe zone has beenreached in the heartbeat cycle. Protection against focusing problemsstemming from concretion movements during breathing is provided whenpulse delivery is permitted only when the physician has activated hisswitch and the breathing cycle signal pickup means 18 has provided anindication that a selected portion of the breathing cycle has beenreached.

Further body functions may be taken into account by further parallelsignal channels, by the rapidly succeeding triggering of several shockwaves by rapidly succeeding trigger pulses witnin one period, and byextracting the trigger pulse only from every second, third, etc. extremevalue.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all suchmodifications.

What is claimed is:
 1. In an apparatus for applying shock wavetreatments to matter located at a place within the body of a patientspaced from the patient's heart by focusing shock waves from a shockwave generator means located outside the patient's body so that suchwaves pass through body tissue to said matter to treat such matter, saidapparatus including means for passing pulses of energy to said generatormeans for generating shock waves, an improved shock wave triggeringsystem for use during the treatment of patients who might be subject toextrasystole stimulation, said triggering system comprisingEKG signalpick up means adapted to respond to the patient's heartbeat cycle, meansoperatively connected to said EKG signal pick up means and to said meansfor passing pulses of energy to said generator means for enablinggeneration of a shock wave only during a safe zone in the S-T intervalof the patient's heartbeat cycle, and manually operable physician'sswitch means operatively connected to said means for passing pulses ofenergy to said generator means for preventing the passage of a pulse tosaid generator means except when the physician has activated said switchmeans, so that a shock wave can be generated only at a time when boththe physician's switch means has been activated and said safe zone hasbeen reached in the heartbeat cycle.
 2. The subject matter of claim 1wherein said triggering system also includes means responsive to thepatient's breathing cycle for enabling generation of a shock wave onlyduring a selected portion of the patient's breathing cycle.
 3. In amethod of applying shock wave treatments to matter located at a placewithin the body of a patient spaced from the patient's heart by focusingshock waves from a shock wave generator located outside the patient'sbody so that such waves pass through body tissue to said matter to treatsuch matter, the improvement oomprising triggering generation of saidshock waves only during time intervals within the patient's heartbeatcycle when the heart is not subject to stimulation into an extrasystole,by monitoring the patient's heartbeat cycle and preventing generation ofa shock wave except at a time within the S-T interval of the heartcycle.
 4. In an apparatus for applying shock wave treatments to matter,located at a place within the body of a patient such that said matter tobe treated is subject to movements as the patient breathes, by focusingshock waves from a shock wave generator means located outside thepatient's body so that such waves pass through body tissue to saidmatter to treat such matter, said apparatus including means for passingpulses of energy to said generator means for generating shock waves, animproved shock wave triggering system for controlling the passage ofpulses of energy to said shock wave generator means so that a shock wavecan be generated only during a selected portion of the patient'sbreathing cycle, said triggering system comprisingsignal pick up meansadapted to respond to the patient's breathing cycle, means operativelyconnected to said signal pick up means and to said means for passingpulses of energy to said generator means for enabling generation of ashock wave only during the selected portion of the patient's breathingcycle, and manually operable physician's switch means operativelyconnected to said means for passing pulses of energy to said generatormeans for preventing the passage of a pulse to said generator meansexcept when the physician has activated said switch means, so that ashock wave can be generated only at a time when both the physician'sswitch means has been activated and said matter has reached a selectedpart of its path of movement in response to the breathing motion of thepatient.
 5. The subject matter of claim 4 wherein said signal pick upmeans includes a respirometer and wherein generation of a shock wave isenabled only during the portion of the breathing cycle whicn followexhalation.
 6. In a method of applying shock wave treatments to matter,located at a place within the body of a patient such that said matter tobe treated is subject to movements as the patient breathes, by focusingshock waves from a shock wave generator located outside the patient'sbody so that such waves pass through body tissue to said matter to treatsuch matter, the improvement comprising triggering generation of shockwaves only during time intervals within the patient's breathing cyclewhen said matter to be treated has reached a selected part of its pathof movement in response to the breathing motion of the patient, bymonitoring the patient's breathing cycle and preventing generation of ashock wave except at a time within a selected part of the breathingcycle.